The EWOD (Electrowetting on Dielectric) display technology is a novel paper display technology that combines the advantages of the ordinary paper and the electronic display technology. The EWOD display technology can realize dynamic display since it is rapid in response time. Compared with active light-emitting panels (e.g., LCDs and AMOLEDs), EWOD display panels do not need any backlight module, so that the EWOD display technology has the characteristic of low power consumption. As one of reflective display technologies, the EWOD display panels only need ambient light for displaying purpose, so the EWOD display panels also have the advantages of high brightness, high contrast and wide angle of view.
In 2003, on Nature, Robert A. Hayes and B. J. Feenstra from Philips firstly proposed the application prospect of EWOD in the display field and provided a prototype design for display devices based on the EWOD technology. FIG. 1 shows the structure of a single-layer EWOD display device commonly used in the art at present. The single-layer EWOD display device consists of a transparent glass or plastic substrate 14, a transparent conducting layer 13, a hydrophobic insulating layer 18, pixel walls 12, a bottom electrode 11, colored ink, colorless liquid 17 (water or ionic liquid), an upper transparent electrode plate 16 coated with a conducting layer, and an encapsulation adhesive 15. When the electro-wetting display device is powered off, nonpolar ink is spread flat on and cover the hydrophobic insulating layer 18, so that the display displays the color of the ink; when a voltage is applied, the original interface balance is changed by an electrostatic force, and the water 17 pushes the ink to a corner, so that light penetrates through the hydrophobic insulating layer 18 and is then reflected by the substrate in white 14, and a white color is displayed. However, since the existing single-layer EWOD electronic paper display device is of a single-layer ink-filled structure and the hydrophobic insulating layer 18 is filled with only one colored ink, only one color (i.e., the color of the filled ink) can be displayed when an electric field is applied. It's hard for the existing single-layer EWOD electronic paper display device to realize full-color displaying, thus it's not comprehensive enough, and the range of applications is small.